1. Field of the Invention
The present invention relates generally to a cam phase control for an internal combustion engine, and more particularly, to a cam phase control apparatus and method, and an engine control unit for an internal combustion engine which rely on a response specifying control algorithm to control an actual cam phase of an intake cam and/or exhaust cam with respect to a crank shaft to converge the actual cam phase to a target cam phase.
2. Description of the Prior Art
A conventional cam phase control apparatus of the type mentioned above is known, for example, from Laid-open Japanese Patent Application No. 2001-132482. An internal combustion engine associated with the cam phase control apparatus comprises a cam phase varying device for changing an actual cam phase of an intake cam. The cam phase varying device comprises a hydraulically driven cam phase varying mechanism, an electromagnetic control valve for supplying the cam phase varying mechanism with an oil pressure from an oil pump, and the like. The cam phase control apparatus in turn comprises a crank angle sensor and a cam angle sensor for detecting signals corresponding to angular positions of a crank shaft and an intake cam, respectively, and a controller which receives the signals detected by these sensors. The controller calculates an actual cam phase based on the signals detected by the crank angle sensor and cam angle sensor, calculates a target cam phase based on an operating condition of the internal combustion engine, and controls the actual cam phase to converge to the target cam phase based on a sliding mode control algorithm which is one type of the response specifying control algorithm.
Specifically, the sliding mode control algorithm models, as a continuous time based model, a controlled object which includes the cam phase varying mechanism and the electromagnetic control valve, and receives a control input to the electromagnetic control valve and outputs a calculated actual cam phase. More specifically, a state equation representative of the controlled object is set as a differential equation which has state variables that represent a first and a second time derivative value of the actual cam phase. A switching function is additionally set as a linear function which has a state variable that represents a deviation of the actual cam phase from the target cam phase, and a time-derivative value (i.e., a changing rate) of the deviation. Then, a control input is calculated such that the deviation and changing rate thereof represented by the state variables of the switching function set in the foregoing manner rest on a switching line, i.e., the control input is calculated such that the deviation and changing rate thereof slide on the switching line to converge to zero, thereby controlling the actual cam phase to converge to the target cam phase.
Generally, the hydraulically driven cam phase varying mechanism exhibits an intense friction characteristic, so that the conventional cam phase varying device preferably controls such a controlled object at a control period as short as possible from a viewpoint of improving the controllability. In addition, since the target cam phase is calculated based on an operating condition of the internal combustion engine, its power spectrum exists in a much lower frequency region than the frequency corresponding to the control period. This means that since the target cam phase is calculated based on a parameter such as the operating condition, accelerator opening, or the like, which changes at a low rate, the calculated target cam phase also changes at a low rate.
Therefore, in the conventional cam phase control apparatus which employs a changing rate of the deviation of the actual cam phase from the target cam phase as a state variable of the switching function, the target cam phase changing at a low rate causes a slow changing rate of the actual cam phase which is controlled based on the target cam phase, so that the changing rate of the deviation of the actual cam phase from the target cam phase lies in the vicinity of zero, if detected at short time intervals such as the control period, meaning that the deviation will remain unchanged. As a result, the calculated deviation is susceptible to noise, and therefore suffers from a low calculation accuracy. Further, the changing rate of the deviation lies in the vicinity of zero so that the switching function is substantially equivalent to the deviation, resulting in a failure in ensuring the robustness and response specifying characteristic due to difficulties in implementing a sliding mode which is unique to the sliding mode control. From the foregoing, the conventional cam phase control apparatus can fall into low controllability in a transient state in which the actual cam phase converges to the target cam phase, possibly causing the actual cam phase to overshoot the target cam phase, by way of example.
Also, since the conventional cam phase control apparatus models a controlled object as a continuous time based model, it is difficult to directly identify model parameters of the controlled object from data derived from an experiment on the controlled object. For this reason, specifically, the continuous time based model must be approximately converted to a discrete time based model to identify the model parameters based on the approximate conversion. However, the use of such an approximation conversion will cause a degraded identification accuracy of the model parameters. Furthermore, since the discrete time based model is again approximately converted to a continuous time based model, increased modeling errors will introduce into the controlled object model due to the xe2x80x9cround-tripxe2x80x9d approximation conversions. Consequently, a controller gain must be limited for ensuring a margin for control stability, resulting in degraded controllability.
The present invention has been made to solve the problems mentioned above, and it is an object of the invention to provide a cam phase control apparatus and method, and an engine control unit for an internal combustion engine which are capable of improving the controllability in a transient state in which an actual cam phase converges to a target cam phase to accurately and readily identify model parameters even when a mechanism for changing the actual cam phase exhibits an intense friction characteristic.
To achieve the above object, according to a first aspect of the present invention, there is provided a cam phase control apparatus for an internal combustion engine for controlling an actual cam phase of at least one of an intake cam and an exhaust cam with respect to a crank shaft.
The cam phase control apparatus according to the first aspect of the present invention is characterized by comprising cam phase varying means for changing the actual cam phase; cam phase detecting means for detecting the actual cam phase; operating condition detecting means for detecting an operating condition of the internal combustion engine; target cam phase setting means for setting a target cam phase in accordance with the detected operating condition; and control means relying on a response specifying control algorithm to determine a control input to the cam phase varying means at a predetermined control period for converging the actual cam phase to the target cam phase, wherein the response specifying control algorithm is configured to model a controlled object which receives the control input to the cam phase varying means and outputs the actual cam phase, and the controlled object is represented by a discrete time based model.
According to this cam phase control apparatus for an internal combustion engine, since the controlled object is modeled as a discrete time based model in the response specifying control algorithm, model parameters can be more accurately and readily identified in accordance with a general identification algorithm such as a least square method based on data obtained from experiments and simulations than the conventional cam phase control apparatus which relies on a continuous time based model. For the same reason, an on-board identifier can be added to the cam phase control apparatus, in which case the model parameters can be appropriately and readily identified in real time to improve the controllability. Further, for the same reason, no approximate conversion is needed for modeling the controlled object, thereby making it possible to reduce a modeling error of the controlled object model and ensure a larger margin for control stability, as compared with the conventional cam phase control apparatus which relies on the continuous time based model, to ensure a larger controller gain and improve the controllability. Also, for the same reason, the cam phase control apparatus of the present invention can accurately specify convergence of the output of the controlled object to a target value, and a frequency response of the output (for example, H control and the like), as authentically intended by the response specifying control algorithm.
To achieve the above object, according to a second aspect of the present invention, there is provided a cam phase control apparatus for an internal combustion engine for controlling an actual cam phase of at least one of an intake cam and an exhaust cam with respect to a crank shaft.
The cam phase control apparatus according to the second aspect of the present invention is characterized by comprising a cam phase varying device for changing the actual cam phase; a cam phase detecting module for detecting the actual cam phase; an operating condition detecting module for detecting an operating condition of the internal combustion engine; a target cam phase setting module for setting a target cam phase in accordance with the detected operating condition; and a control module relying on a response specifying control algorithm to determine a control input to the cam phase varying device at a predetermined control period for converging the actual cam phase to the target cam phase, wherein the response specifying control algorithm is configured to model a controlled object which receives the control input to the cam phase varying device and outputs the actual cam phase, the controlled object is represented by a discrete time based model.
This cam phase control apparatus provides the same advantageous effects as described above concerning the cam phase control apparatus according to the first aspect of the invention.
To achieve the above object, according to a third aspect of the present invention, there is provided a cam phase control apparatus for an internal combustion engine for controlling an actual cam phase of at least one of an intake cam and an exhaust cam with respect to a crank shaft.
The cam phase control method according to the third aspect of the present invention is characterized by comprising the steps of changing the actual cam phase; detecting the actual cam phase; detecting an operating condition of the internal combustion engine; setting a target cam phase in accordance with the detected operating condition; and determining a control input at a predetermined control period in accordance with a response specifying control algorithm for converging the actual cam phase to the target cam phase, wherein the response specifying control algorithm is configured to model a controlled object which receives the control input and outputs the actual cam phase, and the controlled object is represented by a discrete time based model.
This cam phase control method provides the same advantageous effects as described above concerning the cam phase control apparatus according to the first aspect of the invention.
To achieve the above object, according to a fourth aspect of the present invention, there is provided an engine control unit including a control program for causing a computer to carry out control of actual cam phase of at least one of an intake cam and an exhaust cam with respect to a crank shaft in an internal combustion engine.
The engine control unit according to the fourth aspect of the present invention is characterized in that the control program causes the computer to change the actual cam phase; detect the actual cam phase; detect an operating condition of the internal combustion engine; set a target cam phase in accordance with the detected operating condition; and determine a control input at a predetermined control period in accordance with a response specifying control algorithm for converging the actual cam phase to the target cam phase, wherein the response specifying control algorithm is configured to model a controlled object which receives the control input and outputs the actual cam phase, and the controlled object is represented by a discrete time based model.
This engine control unit provides the same advantageous effects as described above concerning the cam phase control apparatus according to the first aspect of the invention.
Preferably, the cam phase control apparatus for an internal combustion engine further comprises sampling means for sampling the control input and the actual cam phase at a predetermined sampling period longer than the control period, wherein the discrete time based model comprises the sampled control input, and time series data of the sampled actual cam phase.
As described above, when this type of cam phase control apparatus attempts to improve the controllability for the cam phase varying means which exhibits an intense friction characteristic, the control input must be determined at a short control period than a predetermined period. On the other hand, in order for the actual cam phase to accurately follow the target cam phase which changes at a low rate, the controlled object model must be matched in frequency characteristic with the actually controlled object in a frequency range which includes the power spectrum of the target cam phase or actual cam phase. Thus, according to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, the sampling means samples the control input and the actual cam phase at a predetermined sampling period longer than the control period, wherein the discrete time based model of the controlled object comprises the control input and time series data of the actual cam phase sampled at this sampling period, so that the dynamic characteristic of the controlled object can be appropriately reflected to the discrete time based model in the frequency range in which the power spectrum of the target cam phase exists. As a result, the controllability can be further improved.
Preferably, the cam phase control apparatus for an internal combustion engine further comprises a sampling module for sampling the control input and the actual cam phase at a predetermined sampling period longer than the control period, wherein the discrete time based model comprises the sampled control input, and time series data of the sampled actual cam phase.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, the cam phase control method for an internal combustion engine further comprises the step of sampling the control input and the actual cam phase at a predetermined sampling period longer than the control period, wherein the discrete time based model comprises the sampled control input, and time series data of the sampled actual cam phase.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the engine control unit, the control program further causes the computer to sample the control input and the actual cam phase at a predetermined sampling period longer than the control period, wherein the discrete time based model comprises the sampled control input, and time series data of the sampled actual cam phase.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the sampling means samples a deviation of the actual cam phase from the target cam phase at the predetermined sampling period, and the control means determines the control input in accordance with a response specifying control algorithm for creating a switching function as a function of time series data of the sampled deviation.
According to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, since the switching function is created as a function of time series data of the sampled deviation of the actual cam phase from the target cam phase, and the sampling period of these time series data is set longer than the control period, a changing amount of the deviation of the actual cam phase to the target cam phase can be appropriately sampled, unlike the conventional cam phase control apparatus which employs a deviation changing rate as a component of a switching function, so that the cam phase control apparatus according to the present invention can more accurately calculate an increase/decrease in the switching function while avoiding the influence of noise to accurately converge the switching function to zero. As a result, when a sliding mode control algorithm is used, for example, as the response specifying control algorithm, a sliding mode can be generated without fail to ensure the robustness and response specifying characteristic which are features of the sliding mode control. For the same reason, when a disturbance such as a counter-force from a cam, for example, is inputted to the controlled object, the sensibility of the switching function to the disturbance can be improved, and the switching function can be calculated as a value which appropriately reflects the influence of the disturbance, so that the control stability can be ensured for the disturbance. In this way, the switching function can be appropriately calculated. From the foregoing, the controllability can be improved over the prior art in a transient state in which the actual cam phase converges to the target cam phase.
Preferably, in the cam phase control apparatus for an internal combustion engine, the sampling module samples a deviation of the actual cam phase from the target cam phase at the predetermined sampling period, and the control module determines the control input in accordance with a response specifying control algorithm for creating a switching function as a function of time series data of the sampled deviation.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the step of sampling includes sampling a deviation of the actual cam phase from the target cam phase at the predetermined sampling period, and the step of controlling includes determining the control input in accordance with a response specifying control algorithm for creating a switching function as a function of time series data of the sampled deviation.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the engine control unit, the control program further causes the computer to sample a deviation of the actual cam phase from the target cam phase at the predetermined sampling period, and determine the control input in accordance with a response specifying control algorithm for creating a switching function as a function of time series data of the sampled deviation.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the response specifying control algorithm is a sliding mode control algorithm.
According to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, when the sliding mode control algorithm is used as the response specifying control algorithm, the resulting cam phase control apparatus excels in the robustness and response specifying characteristic.
Preferably, in the cam phase control apparatus for an internal combustion engine, the response specifying control algorithm is a sliding mode control algorithm.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the response specifying control algorithm is a sliding mode control algorithm.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the engine control unit, the response specifying control algorithm is a sliding mode control algorithm.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the control input comprises a total sum of a plurality of inputs, each of which is determined in accordance with at least one of a value of the switching function and the actual cam phase.
In this type of sliding mode control apparatus, the control input is made up of the total sum of a plurality of inputs which is determined in accordance with the value of the switching function and/or the output of the controlled object (see, for example, Laid-open Japanese Patent Application No. 11-153051). Therefore, according to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, by appropriately setting a plurality of inputs, a state variable of the switching function, i.e., the values of the time series data of the deviation can be carried on a switching hyperplane, thereby converging the deviation to zero. As a result, the actual cam phase can be appropriately converged to the target cam phase.
Preferably, in the cam phase control apparatus for an internal combustion engine, the control input comprises a total sum of a plurality of inputs, each of which is determined in accordance with at least one of a value of the switching function and the actual cam phase.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the control input comprises a total sum of a plurality of inputs, each of which is determined in accordance with at least one of a value of the switching function and the actual cam phase.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the engine control unit, the control input comprises a total sum of a plurality of inputs, each of which is determined in accordance with at least one of a value of the switching function and the actual cam phase.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the plurality of inputs include a reaching law input proportional to the value of the switching function.
It has been theoretically confirmed that in the sliding mode control algorithm, the value of a state variable of the switching function can be rapidly returned onto the switching hyperplane by virtue of the reaching law input proportional to the value of the switching function, included in the control input, even if the state variable of the switching function largely deviates from the switching hyperplane (or a switching line) due to the influence of a large disturbance and the like (see, for example, Laid-open Japanese Patent Application No. 11-153051). Therefore, this preferred embodiment of the cam phase control apparatus for an internal combustion engine can rapidly return the deviation of the actual cam phase from the target cam phase, as a state variable of the switching function, onto the switching hyperplane to rapidly converge the deviation to zero, thereby ensuring the quick responsibility of the control.
Preferably, in the cam phase control apparatus for an internal combustion engine, the plurality of inputs include a reaching law input proportional to the value of the switching function.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the plurality of inputs include a reaching law input proportional to the value of the switching function.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the engine control unit, the plurality of inputs include a reaching law input proportional to the value of the switching function.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the plurality of inputs include a non-linear input which is set inverse in sign to the value of the switching function.
It has been theoretically confirmed that in the sliding mode control algorithm, a state variable of the switching function can be carried on the switching hyperplane by virtue of a non-linear input which is set inverse in sign to the value of the switching function, included in the control inputs, thereby appropriately suppressing a modeling error and the influence of disturbance as well as compensating the controlled object for the non-linear characteristic in accordance thereto (see, for example, Laid-open Japanese Patent Application No. 11-153051). Therefore, this preferred embodiment of the cam phase control apparatus for an internal combustion engine can suppress the modeling error and influence of disturbance as well as compensate the controlled object for the non-linear characteristic in accordance thereto.
Preferably, in the cam phase control apparatus for an internal combustion engine, the plurality of inputs include a non-linear input which is set inverse in sign to the value of the switching function.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the plurality of inputs include a non-linear input which is set inverse in sign to the value of the switching function.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the engine control unit, the plurality of inputs include a non-linear input which is set inverse in sign to the value of the switching function.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the cam phase varying means comprises an electrically driven spool valve including two hydraulic systems for outputting separate oil pressures respectively from an oil pressure source, and a spool valve body movable within a predetermined movable range including a neutral position at which a differential pressure between the oil pressures in the two hydraulic systems is zero, and responsive to the control input for moving the spool valve body within the movable range to change the differential pressure between the oil pressures in the two hydraulic systems; and a cam phase varying mechanism for changing the actual cam phase in accordance with the differential pressure between the oil pressures in the two hydraulic systems outputted from the electrically movable spool valve, wherein the plurality of inputs include a non-linear input which is set inverse in sign to the value of the switching function, and the non-linear input has a gain which is set in accordance with the differential pressure between the oil pressures in the two hydraulic systems.
In this type of electrically driven spool valve, two oil pressures outputted respectively from the two hydraulic systems generally exhibit non-linear characteristics to the position of the spool valve body within the movable range, i.e., a differential pressure between the oil pressures in the two hydraulic systems. As such, the actual cam phase, which is the output of the cam phase varying means, also generally exhibits a non-linear characteristic. On the other hand, according to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, since the gain of the non-linear input is set in accordance with the pressure difference between the oil pressures in the two hydraulic systems, the cam phase varying means can be appropriately compensated for the non-linear output characteristic in accordance therewith.
Preferably, in the cam phase control apparatus for an internal combustion engine, the cam phase varying device comprises an electrically driven spool valve including two hydraulic systems for outputting separate oil pressures respectively from an oil pressure source, and a spool valve body movable within a predetermined movable range including a neutral position at which a differential pressure between the oil pressures in the two hydraulic systems is zero, and responsive to the control input for moving the spool valve body within the movable range to change the differential pressure between the oil pressures in the two hydraulic systems; and a cam phase varying mechanism for changing the actual cam phase in accordance with the differential pressure between the oil pressures in the two hydraulic systems outputted from the electrically movable spool valve, wherein the plurality of inputs include a non-linear input which is set inverse in sign to the value of the switching function, and the non-linear input has a gain which is set in accordance with the differential pressure between the oil pressures in the two hydraulic systems.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the step of changing the actual cam phase includes changing a differential pressure between oil pressures in two hydraulic systems from an oil pressure source in response to the control input; and changing the actual cam phase in accordance with the differential pressure between the oil pressures in the two hydraulic systems, wherein the plurality of inputs include a non-linear input which is set inverse in sign to the value of the switching function, and the non-linear input has a gain which is set in accordance with the differential pressure between the oil pressures in the two hydraulic systems.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the engine control unit, the control program further causes the computer to change a differential pressure between oil pressures in two hydraulic systems from an oil pressure source in response to the control input; and change the actual cam phase in accordance with the differential pressure between the oil pressures in the two hydraulic systems, wherein the plurality of inputs include a non-linear input which is set inverse in sign to the value of the switching function, and the non-linear input has a gain which is set in accordance with the differential pressure between the oil pressures in the two hydraulic systems.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the gain of the non-linear input is set to a larger value when the differential pressure between the oil pressures in the two hydraulic systems is within a predetermined range including zero than when the differential pressure is not within the predetermined range.
Generally, this type of electrically driven spool valve is most instable in behavior when the spool valve body is near the neutral position, i.e., when the differential pressure between the oil pressures in the two hydraulic systems is near zero, due to the most prominent non-linear characteristic. On the other hand, according to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, since the gain of the non-linear input is set to a larger value when the differential pressure between the oil pressures in the two hydraulic systems is within a predetermined range including zero than when not within the predetermined range, the gain of the non-linear input can be set larger when the non-linear characteristic becomes most prominent by appropriately setting this predetermined range. Consequently, the electrically driven spool valve can be more effectively and appropriately compensated for the non-linear characteristic.
Preferably, in the cam phase control apparatus for an internal combustion engine, the gain of the non-linear input is set to a larger value when the differential pressure between the oil pressures in the two hydraulic systems is within a predetermined range including zero than when the differential pressure is not within the predetermined range.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the gain of the non-linear input is set to a larger value when the differential pressure between the oil pressures in the two hydraulic systems is within a predetermined range including zero than when the differential pressure is not within the predetermined range.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the engine control unit, the gain of the non-linear input is set to a larger value when the differential pressure between the oil pressures in the two hydraulic systems is within a predetermined range including zero than when the differential pressure is not within the predetermined range.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the plurality of inputs include a damping input which is proportional to a rate at which the actual cam phase is changed.
Generally, in the cam phase varying device, the actual cam phase is more likely to overshoot the target cam phase due to the inertia of mechanical parts when the target cam phase is changing at a high rate. On the other hand, according to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, since the control inputs include the damping input which is proportional to the rate at which the actual cam phase changes, the actual cam phase can be appropriately prevented from overshooting the target cam phase in accordance with the changing rate. Particularly, when the actual cam phase is more susceptible to the overshooting due to the inertia of the hydraulic systems and the compressivity of the oil resulting from the hydraulically driven cam phase varying device, the actual cam phase can be effectively prevented from overshooting the target cam phase.
Preferably, in the cam phase control apparatus for an internal combustion engine, the plurality of inputs include a damping input which is proportional to a rate at which the actual cam phase is changed.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the plurality of inputs include a damping input which is proportional to a rate at which the actual cam phase is changed.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the engine control unit, the plurality of inputs include a damping input which is proportional to a rate at which the actual cam phase is changed.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the plurality of inputs include an adaptive law input which is proportional to an integrated value of the switching function.
In a so-called adaptive sliding mode control algorithm in which the control inputs include an adaptive law input which is proportional to an integrated value of the switching function, it is theoretically confirmed that the adaptive law input can help carry the value of a state variable of the switching function on the switching hyperplane without fail, while suppressing a steady-state deviation of the controlled object, a modeling error, and the influence of disturbance (see, for example, Laid-open Japanese Patent Application No. 11-153051). Therefore, this preferred embodiment of the cam phase control apparatus for an internal combustion engine can carry the time series data of the deviation of the actual cam phase from the target cam phase on the switching hyperplane, while suppressing the steady-state deviation of the controlled object, modeling error, and influence of disturbance, thereby converging the deviation to zero without fail. In other words, the cam phase control apparatus for an internal combustion engine can ensure the stability of the control against the steady-state deviation of the controlled object, modeling error, and influence of disturbance.
Preferably, in the cam phase control apparatus for an internal combustion engine, the plurality of inputs include an adaptive law input which is proportional to an integrated value of the switching function.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the plurality of inputs include an adaptive law input which is proportional to an integrated value of the switching function.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the engine control unit, the plurality of inputs include an adaptive law input which is proportional to an integrated value of the switching function.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the adaptive law input has a gain which is set in accordance with the value of the switching function.
According to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, since the gain of the adaptive law input is set in accordance with the value of the switching function, it is possible to appropriately prevent the actual cam phase from overshooting the target cam phase, due to the integration characteristic of the adaptive law input.
Preferably, in the cam phase control apparatus for an internal combustion engine, the adaptive law input has a gain which is set in accordance with the value of the switching function.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the adaptive law input has a gain which is set in accordance with the value of the switching function.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the engine control unit, the adaptive law input has a gain which is set in accordance with the value of the switching function.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the plurality of inputs include an equivalent control input which is determined based on a plurality of values of actual cam phases sequentially sampled at the predetermined sampling period.
It has been theoretically confirmed that in the sliding mode control algorithm, an equivalent control input included in the control inputs can help securely restrict a state variable of the switching function on the switching hyperplane (see, for example, Laid-open Japanese Patent Application No. 11-153051). Therefore, according to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, the time series data of the deviation as a state variable of the switching function can be securely restricted on the switching hyperplane, thereby converging the actual cam phase to the target cam phase without fail (i.e., converging the deviation to zero), and maintaining a stable behavior of the actual cam phase after the convergence. In addition, when the sampling period of the actual cam phase is set longer than the control period in the aforementioned preferred embodiment, the dynamic characteristic of the actual cam phase can be appropriately reflected to the equivalent control input near the frequency range in which the power spectrum of the target cam phase exists by appropriately setting the sampling period of the actual cam phase in accordance with the frequency range, even when the cam phase varying device exhibits an intense friction characteristic. Consequently, the stability can be ensured in controlling the actual cam phase near the frequency range in which the power spectrum of the target cam phase exists.
Preferably, in the cam phase control apparatus for an internal combustion engine, the plurality of inputs include an equivalent control input which is determined based on a plurality of values of actual cam phases sequentially sampled at the predetermined sampling period.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the plurality of inputs include an equivalent control input which is determined based on a plurality of values of actual cam phases sequentially sampled at the predetermined sampling period.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the engine control unit, the plurality of inputs include an equivalent control input which is determined based on a plurality of values of actual cam phases sequentially sampled at the predetermined sampling period.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the plurality of inputs include at least one input which has a gain scheduled in different manners from each other when the actual cam phase is advanced and when the actual cam phase is retarded.
According to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, even if the actual cam phase responses to the control input in different manners when it is advanced and when it is retarded, the actual cam phase can be compensated for the responsibility such that the same responsibility is provided when the actual cam phase is advanced or retarded.
Preferably, in the cam phase control apparatus for an internal combustion engine, the plurality of inputs include at least one input which has a gain scheduled in different manners from each other when the actual cam phase is advanced and when the actual cam phase is retarded.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the plurality of inputs include at least one input which has a gain scheduled in different manners from each other when the actual cam phase is advanced and when the actual cam phase is retarded.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the engine control unit, the plurality of inputs include at least one input which has a gain scheduled in different manners from each other when the actual cam phase is advanced and when the actual cam phase is retarded.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the cam phase varying means is configured to change the actual cam phase with an oil pressure supplied from an oil pressure source, at least one of the time series data of the deviation making up the switching function is multiplied by a multiplication coefficient, and the multiplication coefficient is set in accordance with the oil pressure supplied from the oil pressure source to the cam phase varying means.
Generally, this type of cam phase varying means presents a change in the dynamic characteristic thereof (dynamic characteristic of the actual cam phase), more specifically, its response characteristic as it is supplied with a varying oil pressure from the oil pressure source. On the other hand, according to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, at least one of the time series data of the deviation, which make up the switching function, is multiplied by the multiplication coefficient set in accordance with the oil pressure supplied from the oil pressure source to appropriately set a rate at which the actual cam phase follows the target cam phase in accordance with the response characteristic of the cam phase varying device, so that the cam phase varying means can appropriately change the actual cam phase while compensating for a change in the response characteristic resulting from a change in the oil pressure, thereby maintaining a stable responsibility of the actual cam phase to the control input. As a result, the internal combustion engine can be maintained in a stable operating condition.
Preferably, in the cam phase control apparatus for an internal combustion engine, the cam phase varying device is configured to change the actual cam phase with an oil pressure supplied from an oil pressure source, at least one of the time series data of the deviation making up the switching function is multiplied by a multiplication coefficient, and the multiplication coefficient is set in accordance with the oil pressure supplied from the oil pressure source to the cam phase varying device.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the step of changing the actual cam phase includes changing the actual cam phase with an oil pressure supplied from an oil pressure source, wherein at least one of the time series data of the deviation making up the switching function is multiplied by a multiplication coefficient, and the multiplication coefficient is set in accordance with the oil pressure supplied from the oil pressure source.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the engine control unit, the control program further causes the computer to change the actual cam phase with an oil pressure supplied from an oil pressure source, multiply at least one of the time series data of the deviation making up the switching function by a multiplication coefficient, and set the multiplication coefficient in accordance with the oil pressure supplied from the oil pressure source.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the multiplication coefficient is set such that the deviation decreases at a lower rate as a differential pressure between the oil pressure and a predetermined reference pressure is larger.
In this type of cam phase varying means, it has been confirmed that the actual cam phase optimally converges to the target cam phase when the oil pressure supplied from the oil pressure source is at a predetermined pressure; more susceptible to overshoot the target cam phase as the oil pressure is higher than the predetermined pressure; and more slowly converges to the target cam phase as the oil pressure is lower than the predetermined pressure (see FIG. 6). Therefore, according to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, with the predetermined reference pressure set as the predetermined pressure as mentioned above, the deviation decreases at a lower rate when the oil pressure is higher than the predetermined reference pressure to prevent the actual cam phase from overshooting the target cam phase, whereas the deviation decreases at a higher rate when the oil pressure is lower than the predetermined reference pressure to appropriately increase the rate at which the actual cam phase converges to the target cam phase.
Preferably, in the cam phase control apparatus for an internal combustion engine, the multiplication coefficient is set such that the deviation decreases at a lower rate as a differential pressure between the oil pressure and a predetermined reference pressure is larger.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the multiplication coefficient is set such that the deviation decreases at a lower rate as a differential pressure between the oil pressure and a predetermined reference pressure is larger.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the engine control unit, the multiplication coefficient is set such that the deviation decreases at a lower rate as a differential pressure between the oil pressure and a predetermined reference pressure is larger.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the oil pressure source supplies the cam phase varying means with an oil used in the internal combustion engine, and the multiplication coefficient is set such that the deviation decreases at a lower rate as a shorter time has elapsed from a start of the internal combustion engine.
Generally, in this type of cam phase varying device, the actual cam phase changes more slowly, as the temperature of the oil supplied from the oil pressure source is lower, due to a larger viscous resistance of the oil. Consequently, a degraded responsibility causes an instable behavior of the actual cam phase. For this reason, a low oil temperature may cause an instable behavior of the actual cam phase immediately after the internal combustion engine is started. On the other hand, according to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, since the rate at which the deviation decreases is set lower as a shorter time has elapsed from the start of the internal combustion engine, the responsibility of the control is made lower as the temperature of the oil is lower to make the actual cam phase more susceptible to an instable behavior, thereby making it possible to appropriately converge the actual cam phase to the target cam phase, while compensating the actual cam phase for an instable condition immediately after the start of the internal combustion engine, to ensure the stability for the control.
Preferably, in the cam phase control apparatus for an internal combustion engine, the oil pressure source supplies the cam phase varying device with an oil used in the internal combustion engine, and the multiplication coefficient is set such that the deviation decreases at a lower rate as a shorter time has elapsed from a start of the internal combustion engine.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the oil pressure source supplies an oil used in the internal combustion engine, and the multiplication coefficient is set such that the deviation decreases at a lower rate as a shorter time has elapsed from a start of the internal combustion engine.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the engine control unit, the oil pressure source supplies an oil used in the internal combustion engine, and the multiplication coefficient is set such that the deviation decreases at a lower rate as a shorter time has elapsed from a start of the internal combustion engine.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the cam phase varying means is configured to change the actual cam phase with an oil supplied from an oil pressure source for use by the internal combustion engine, at least one of the time series data of the deviation making up the switching function is multiplied by a multiplication coefficient, and the multiplication coefficient is set such that the deviation decreases at a lower rate as a shorter time has elapsed from a start of the internal combustion engine.
According to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, since the rate at which the deviation decreases is set lower as a shorter time has elapsed from the start of the internal combustion engine, the responsibility of the control is made lower as the temperature of the oil is lower to make the actual cam phase more susceptible to an instable behavior, thereby making it possible to appropriately converge the actual cam phase to the target cam phase, while compensating the actual cam phase for an instable condition immediately after the start of the internal combustion engine, to ensure the stability for the control.
Preferably, in the cam phase control apparatus for an internal combustion engine, the cam phase varying device is configured to change the actual cam phase with an oil supplied from an oil pressure source for use by the internal combustion engine, at least one of the time series data of the deviation making up the switching function is multiplied by a multiplication coefficient, and the multiplication coefficient is set such that the deviation decreases at a lower rate as a shorter time has elapsed from a start of the internal combustion engine.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the step of changing the actual cam phase includes changing the actual cam phase with an oil supplied from an oil pressure source for use by the internal combustion engine, wherein at least one of the time series data of the deviation making up the switching function is multiplied by a multiplication coefficient, and the multiplication coefficient is set such that the deviation decreases at a lower rate as a shorter time has elapsed from a start of the internal combustion engine.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
Preferably, in the engine control unit, the control program further causes the computer to change the actual cam phase with an oil supplied from an oil pressure source for use by the internal combustion engine, multiply at least one of the time series data of the deviation making up the switching function by a multiplication coefficient, and set the multiplication coefficient such that the deviation decreases at a lower rate as a shorter time has elapsed from a start of the internal combustion engine.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the first aspect of the invention.
To achieve the above object, according to a fifth aspect of the present invention, there is provided a cam phase control apparatus for an internal combustion engine for controlling an actual cam phase of at least one of an intake cam and an exhaust cam with respect to a crank shaft.
The cam phase control apparatus for an internal combustion engine according to the fifth aspect of the invention is characterized by comprising cam phase varying means for changing the actual cam phase; cam phase detecting means for detecting the actual cam phase; operating condition detecting means for detecting an operating condition of the internal combustion engine; target cam phase setting means for setting a target cam phase in accordance with the detected operating condition; sampling means for sampling a deviation of the detected actual cam phase from the set target cam phase at a predetermined sampling period; and control means relying on a response specifying control algorithm for creating a switching function as a function of time series data of the sampled deviation to determine a control input to the cam phase varying means at a predetermined control period for converging the actual cam phase to the target cam phase.
According to this cam phase control apparatus for an internal combustion engine, since the switching function is set as a function of time series data of the deviation of the actual cam phase from the target cam phase, sampled at the predetermined sampling period, the deviation of the actual cam phase from the target cam phase can be sampled as a value to which an increase/decrease behavior of the deviation is appropriately reflected in the frequency range in which the power spectrum of the target cam phase exists by appropriately setting the sampling period of the time series data. Thus, unlike the conventional cam phase control apparatus which employs a deviation changing rate as a component of a switching function, the switching function can be appropriately calculated while avoiding the influence of noise even when the cam phase varying device exhibits, for example, an intense friction characteristic, and the control input is calculated at a control period shorter than a period which corresponds to the frequency range in which the power spectrum of the target cam phase exists, thereby increasing the responsibility in a transient state in which the actual cam phase converges to the target cam phase.
To achieve the above object, according to a sixth aspect of the present invention, there is provided a cam phase control apparatus for an internal combustion engine for controlling an actual cam phase of at least one of an intake cam and an exhaust cam with respect to a crank shaft.
The cam phase control apparatus for an internal combustion engine according to the sixth aspect of the invention is characterized by comprising a cam phase varying device for changing the actual cam phase; a cam phase detecting module for detecting the actual cam phase; an operating condition detecting module for detecting an operating condition of the internal combustion engine; a target cam phase setting module for setting a target cam phase in accordance with the detected operating condition; a sampling module for sampling a deviation of the detected actual cam phase from the set target cam phase at a predetermined sampling period; and a control module relying on a response specifying control algorithm for creating a switching function as a function of time series data of the sampled deviation to determine a control input to the cam phase varying device at a predetermined control period for converging the actual cam phase to the target cam phase.
This cam phase control apparatus provides the same advantageous effects as described above concerning the cam phase control apparatus according to the fifth aspect of the invention.
To achieve the above object, according to a seventh aspect of the present invention, there is provided a cam phase control apparatus for an internal combustion engine for controlling an actual cam phase of at least one of an intake cam and an exhaust cam with respect to a crank shaft.
The cam phase control method according to the seventh aspect of the present invention is characterized by comprising the steps of changing the actual cam phase; detecting the actual cam phase; detecting an operating condition of the internal combustion engine; setting a target cam phase in accordance with the detected operating condition; sampling a deviation of the detected actual cam phase from the set target cam phase at a predetermined sampling period; and determining a control input at a predetermined control period in accordance with a response specifying control algorithm for creating a switching function as a function of time series data of the sampled deviation for converging the actual cam phase to the target cam phase.
This cam phase control method provides the same advantageous effects as described above concerning the cam phase control apparatus according to the fifth aspect of the invention.
To achieve the above object, according to an eighth aspect of the present invention, there is provided an engine control unit including a control program for causing a computer to carry out control of actual cam phase of at least one of an intake cam and an exhaust cam with respect to a crank shaft in an internal combustion engine.
The engine control unit according to the eighth aspect of the present invention is characterized in that the control program causes the computer to change the actual cam phase; detect the actual cam phase; detect an operating condition of the internal combustion engine; set a target cam phase in accordance with the detected operating condition; sample a deviation of the detected actual cam phase from the set target cam phase at a predetermined sampling period; and determine a control input at a predetermined control period in accordance with a response specifying control algorithm for creating a switching function as a function of time series data of the sampled deviation for converging the actual cam phase to the target cam phase.
This cam phase control apparatus provides the same advantageous effects as described above concerning the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the predetermined sampling period is set longer than the control period.
According to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, since the switching function is created as a function of time series data of the sampled deviation of the actual cam phase from the target cam phase, and the sampling period of these time series data is set longer than the control period, a changing amount of the deviation of the actual cam phase to the target cam phase can be appropriately sampled, unlike the conventional cam phase control apparatus which employs a deviation changing rate as a component of a switching function, so that the cam phase control apparatus according to the present invention can more accurately calculate an increase/decrease in the switching function while avoiding the influence of noise to accurately converge the switching function to zero. As a result, when a sliding mode control algorithm is used, for example, as the response specifying control algorithm, a sliding mode can be generated without fail to ensure the robustness and response specifying characteristic which are features of the sliding mode control. For the same reason, when a disturbance such as a counter-force from a cam, for example, is inputted to the controlled object, the sensibility of the switching function to the disturbance can be improved, and the switching function can be calculated as a value which appropriately reflects the influence of the disturbance, so that the control stability can be ensured for the disturbance. In this way, the switching function can be appropriately calculated. From the foregoing, the controllability can be improved over the prior art in a transient state in which the actual cam phase converges to the target cam phase.
Preferably, in the cam phase control apparatus for an internal combustion engine, the predetermined sampling period is set longer than the control period.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the predetermined sampling period is set longer than the control period.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the engine control unit, the predetermined sampling period is set longer than the control period.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the response specifying control algorithm is a sliding mode control algorithm.
According to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, when the sliding mode control algorithm is used as the response specifying control algorithm, the resulting cam phase control apparatus excels in the robustness and response specifying characteristic.
Preferably, in the cam phase control apparatus for an internal combustion engine, the response specifying control algorithm is a sliding mode control algorithm.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the response specifying control algorithm is a sliding mode control algorithm.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the engine control unit, the response specifying control algorithm is a sliding mode control algorithm.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the control input comprises a total sum of a plurality of inputs, each of which is determined in accordance with at least one of a value of the switching function and the actual cam phase.
In this type of sliding mode control apparatus, the control input is made up of the total sum of a plurality of inputs which is determined in accordance with the value of the switching function and/or the output of the controlled object (see, for example, Laid-open Japanese Patent Application No. 11-153051). Therefore, according to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, by appropriately setting a plurality of inputs, a state variable of the switching function, i.e., the values of the time series data of the deviation can be carried on a switching hyperplane, thereby converging the deviation to zero. As a result, the actual cam phase can be appropriately converged to the target cam phase.
Preferably, in the cam phase control apparatus for an internal combustion engine, the control input comprises a total sum of a plurality of inputs, each of which is determined in accordance with at least one of a value of the switching function and the actual cam phase.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the control input comprises a total sum of a plurality of inputs, each of which is determined in accordance with at least one of a value of the switching function and the actual cam phase.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the engine control unit, the control input comprises a total sum of a plurality of inputs, each of which is determined in accordance with at least one of a value of the switching function and the actual cam phase.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the plurality of inputs include a reaching law input proportional to the value of the switching function.
It has been theoretically confirmed that in the sliding mode control algorithm, the value of a state variable of the switching function can be rapidly returned onto the switching hyperplane by virtue of the reaching law input proportional to the value of the switching function, included in the control input, even if the state variable of the switching function largely deviates from the switching hyperplane (or a switching line) due to the influence of a large disturbance and the like (see, for example, Laid-open Japanese Patent Application No. 11-153051). Therefore, this preferred embodiment of the cam phase control apparatus for an internal combustion engine can rapidly return the deviation of the actual cam phase from the target cam phase, as a state variable of the switching function, onto the switching hyperplane to rapidly converge the deviation to zero, thereby ensuring the quick responsibility of the control.
Preferably, in the cam phase control apparatus for an internal combustion engine, the plurality of inputs include a reaching law input proportional to the value of the switching function.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the plurality of inputs include a reaching law input proportional to the value of the switching function.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the engine control unit, the plurality of inputs include a reaching law input proportional to the value of the switching function.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the plurality of inputs include a non-linear input which is set inverse in sign to the value of the switching function.
It has been theoretically confirmed that in the sliding mode control algorithm, a state variable of the switching function can be carried on the switching hyperplane by virtue of a non-linear input which is set inverse in sign to the value of the switching function, included in the control inputs, thereby appropriately suppressing a modeling error and the influence of disturbance as well as compensating the controlled object for the non-linear characteristic in accordance thereto (see, for example, Laid-open Japanese Patent Application No. 11-153051). Therefore, this preferred embodiment of the cam phase control apparatus for an internal combustion engine can suppress the modeling error and influence of disturbance as well as compensate the controlled object for the non-linear characteristic in accordance thereto.
Preferably, in the cam phase control apparatus for an internal combustion engine, the plurality of inputs include a non-linear input which is set inverse in sign to the value of the switching function.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the plurality of inputs include a non-linear input which is set inverse in sign to the value of the switching function.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the engine control unit, the plurality of inputs include a non-linear input which is set inverse in sign to the value of the switching function.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the cam phase varying means comprises an electrically driven spool valve including two hydraulic systems for outputting separate oil pressures respectively from an oil pressure source, and a spool valve body movable within a predetermined movable range including a neutral position at which a differential pressure between the oil pressures in the two hydraulic systems is zero, and responsive to the control input for moving the spool valve body within the movable range to change the differential pressure between the oil pressures in the two hydraulic systems; and a cam phase varying mechanism for changing the actual cam phase in accordance with the differential pressure between the oil pressures in the two hydraulic systems outputted from the electrically movable spool valve, wherein the plurality of inputs include a non-linear input which is set inverse in sign to the value of the switching function, and the non-linear input has a gain which is set in accordance with the differential pressure between the oil pressures in the two hydraulic systems.
In this type of electrically driven spool valve, two oil pressures outputted respectively from the two hydraulic systems generally exhibit non-linear characteristics to the position of the spool valve body within the movable range, i.e., a differential pressure between the oil pressures in the two hydraulic systems. As such, the actual cam phase, which is the output of the cam phase varying means, also generally exhibits a non-linear characteristic. On the other hand, according to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, since the gain of the non-linear input is set in accordance with the pressure difference between the oil pressures in the two hydraulic systems, the cam phase varying means can be appropriately compensated for the non-linear output characteristic in accordance therewith.
Preferably, in the cam phase control apparatus for an internal combustion engine, the cam phase varying device comprises an electrically driven spool valve including two hydraulic systems for outputting separate oil pressures respectively from an oil pressure source, and a spool valve body movable within a predetermined movable range including a neutral position at which a differential pressure between the oil pressures in the two hydraulic systems is zero, and responsive to the control input for moving the spool valve body within the movable range to change the differential pressure between the oil pressures in the two hydraulic systems; and a cam phase varying mechanism for changing the actual cam phase in accordance with the differential pressure between the oil pressures in the two hydraulic systems outputted from the electrically movable spool valve, wherein the plurality of inputs include a non-linear input which is set inverse in sign to the value of the switching function, the non-linear input having a gain which is set in accordance with the differential pressure between the oil pressures in the two hydraulic systems.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the step of changing the actual cam phase includes changing a differential pressure between oil pressures in two hydraulic systems from an oil pressure source in response to the control input; and changing the actual cam phase in accordance with the differential pressure between the oil pressures in the two hydraulic systems, wherein the plurality of inputs include a non-linear input which is set inverse in sign to the value of the switching function, the non-linear input having a gain which is set in accordance with the differential pressure between the oil pressures in the two hydraulic systems.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the engine control unit, the control program further causes the computer to change a differential pressure between oil pressures in two hydraulic systems from an oil pressure source in response to the control input; and change the actual cam phase in accordance with the differential pressure between the oil pressures in the two hydraulic systems, wherein the plurality of inputs include a non-linear input which is set inverse in sign to the value of the switching function, the non-linear input having a gain which is set in accordance with the differential pressure between the oil pressures in the two hydraulic systems.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the gain of the non-linear input is set to a larger value when the differential pressure between the oil pressures in the two hydraulic systems is within a predetermined range including zero than when the differential pressure is not within the predetermined range.
Generally, this type of electrically driven spool valve is most instable in behavior when the spool valve body is near the neutral position, i.e., when the differential pressure between the oil pressures in the two hydraulic systems is near zero, due to the most prominent non-linear characteristic. On the other hand, according to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, since the gain of the non-linear input is set to a larger value when the differential pressure between the oil pressures in the two hydraulic systems is within a predetermined range including zero than when not within the predetermined range, the gain of the non-linear input can be set larger when the non-linear characteristic becomes most prominent by appropriately setting this predetermined range. Consequently, the electrically driven spool valve can be more effectively and appropriately compensated for the non-linear characteristic.
Preferably, in the cam phase control apparatus for an internal combustion engine, the gain of the non-linear input is set to a larger value when the differential pressure between the oil pressures in the two hydraulic systems is within a predetermined range including zero than when the differential pressure is not within the predetermined range.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the gain of the non-linear input is set to a larger value when the differential pressure between the oil pressures in the two hydraulic systems is within a predetermined range including zero than when the differential pressure is not within the predetermined range.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the engine control unit, the gain of the non-linear input is set to a larger value when the differential pressure between the oil pressures in the two hydraulic systems is within a predetermined range including zero than when the differential pressure is not within the predetermined range.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the plurality of inputs include a damping input which is proportional to a rate at which the actual cam phase is changed.
Generally, in the cam phase varying device, the actual cam phase is more likely to overshoot the target cam phase due to the inertia of mechanical parts when the target cam phase is changing at a high rate. On the other hand, according to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, since the control inputs include the damping input which is proportional to the rate at which the actual cam phase changes, the actual cam phase can be appropriately prevented from overshooting the target cam phase in accordance with the changing rate. Particularly, when the actual cam phase is more susceptible to the overshooting due to the inertia of the hydraulic systems and the compressivity of the oil resulting from the hydraulically driven cam phase varying device, the actual cam phase can be effectively prevented from overshooting the target cam phase.
Preferably, in the cam phase control apparatus for an internal combustion engine, the plurality of inputs include a damping input which is proportional to a rate at which the actual cam phase is changed.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the plurality of inputs include a damping input which is proportional to a rate at which the actual cam phase is changed.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the engine control unit, the plurality of inputs include a damping input which is proportional to a rate at which the actual cam phase is changed.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the plurality of inputs include an adaptive law input which is proportional to an integrated value of the switching function.
In a so-called adaptive sliding mode control algorithm in which the control inputs include an adaptive law input which is proportional to an integrated value of the switching function, it is theoretically confirmed that the adaptive law input can help carry the value of a state variable of the switching function on the switching hyperplane without fail, while suppressing a steady-state deviation of the controlled object, a modeling error, and the influence of disturbance (see, for example, Laid-open Japanese Patent Application No. 11-153051). Therefore, this preferred embodiment of the cam phase control apparatus for an internal combustion engine can carry the time series data of the deviation of the actual cam phase from the target cam phase on the switching hyperplane, while suppressing the steady-state deviation of the controlled object, modeling error, and influence of disturbance, thereby converging the deviation to zero without fail. In other words, the cam phase control apparatus for an internal combustion engine can ensure the stability of the control against the steady-state deviation of the controlled object, modeling error, and influence of disturbance.
Preferably, in the cam phase control apparatus for an internal combustion engine, the plurality of inputs include an adaptive law input which is proportional to an integrated value of the switching function.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the plurality of inputs include an adaptive law input which is proportional to an integrated value of the switching function.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the engine control unit, the plurality of inputs include an adaptive law input which is proportional to an integrated value of the switching function.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the adaptive law input has a gain which is set in accordance with the value of the switching function.
According to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, since the gain of the adaptive law input is set in accordance with the value of the switching function, it is possible to appropriately prevent the actual cam phase from overshooting the target cam phase, due to the integration characteristic of the adaptive law input.
Preferably, in the cam phase control apparatus for an internal combustion engine, the adaptive law input has a gain which is set in accordance with the value of the switching function.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the adaptive law input has a gain which is set in accordance with the value of the switching function.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the engine control unit, the adaptive law input has a gain which is set in accordance with the value of the switching function.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the sampling means further samples the actual cam phase at the predetermined sampling period, and the plurality of inputs include an equivalent control input which is determined based on a plurality of values of actual cam phases sequentially sampled at the predetermined sampling period.
It has been theoretically confirmed that in the sliding mode control algorithm, an equivalent control input included in the control inputs can help securely restrict a state variable of the switching function on the switching hyperplane (see, for example, Laid-open Japanese Patent Application No. 11-153051). Therefore, according to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, the time series data of the deviation as a state variable of the switching function can be securely restricted on the switching hyperplane, thereby converging the actual cam phase to the target cam phase without fail (i.e., converging the deviation to zero), and maintaining a stable behavior of the actual cam phase after the convergence. In addition, when the sampling period of the actual cam phase is set longer than the control period in the aforementioned preferred embodiment, the dynamic characteristic of the actual cam phase can be appropriately reflected to the equivalent control input near the frequency range in which the power spectrum of the target cam phase exists by appropriately setting the sampling period of the actual cam phase in accordance with the frequency range, even when the cam phase varying device exhibits an intense friction characteristic. Consequently, the stability can be ensured in controlling the actual cam phase near the frequency range in which the power spectrum of the target cam phase exists.
Preferably, in the cam phase control apparatus for an internal combustion engine, the sampling module further samples the actual cam phase at the predetermined sampling period, and the plurality of inputs include an equivalent control input which is determined based on a plurality of values of actual cam phases sequentially sampled at the predetermined sampling period.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the step of sampling further includes sampling the actual cam phase at the predetermined sampling period, and the plurality of inputs include an equivalent control input which is determined based on a plurality of values of actual cam phases sequentially sampled at the predetermined sampling period.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the engine control unit, the control program further causes the computer to sample the actual cam phase at the predetermined sampling period, and the plurality of inputs include an equivalent control input which is determined based on a plurality of values of actual cam phases sequentially sampled at the predetermined sampling period.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the plurality of inputs include at least one input which has a gain scheduled in different manners from each other when the actual cam phase is advanced and when the actual cam phase is retarded.
According to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, even if the actual cam phase responses to the control input in different manners when it is advanced and when it is retarded, the actual cam phase can be compensated for the responsibility such that the same responsibility is provided when the actual cam phase is advanced or retarded.
Preferably, in the cam phase control apparatus for an internal combustion engine, the plurality of inputs include at least one input which has a gain scheduled in different manners from each other when the actual cam phase is advanced and when the actual cam phase is retarded.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the plurality of inputs include at least one input which has a gain scheduled in different manners from each other when the actual cam phase is advanced and when the actual cam phase is retarded.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the engine control unit, the plurality of inputs include at least one input which has a gain scheduled in different manners from each other when the actual cam phase is advanced and when the actual cam phase is retarded.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the cam phase varying means is configured to change the actual cam phase with an oil pressure supplied from an oil pressure source, at least one of the time series data of the deviation making up the switching function is multiplied by a multiplication coefficient, and the multiplication coefficient is set in accordance with the oil pressure supplied from the oil pressure source to the cam phase varying means.
Generally, this type of cam phase varying means presents a change in the dynamic characteristic thereof (dynamic characteristic of the actual cam phase), more specifically, its response characteristic as it is supplied with a varying oil pressure from the oil pressure source. On the other hand, according to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, at least one of the time series data of the deviation, which make up the switching function, is multiplied by the multiplication coefficient set in accordance with the oil pressure supplied from the oil pressure source to appropriately set a rate at which the actual cam phase follows the target cam phase in accordance with the response characteristic of the cam phase varying device, so that the cam phase varying means can appropriately change the actual cam phase while compensating for a change in the response characteristic resulting from a change in the oil pressure, thereby maintaining a stable responsibility of the actual cam phase to the control input. As a result, the internal combustion engine can be maintained in a stable operating condition.
Preferably, in the cam phase control apparatus for an internal combustion engine, the cam phase varying device is configured to change the actual cam phase with an oil pressure supplied from an oil pressure source, at least one of the time series data of the deviation making up the switching function is multiplied by a multiplication coefficient, and the multiplication coefficient is set in accordance with the oil pressure supplied from the oil pressure source to the cam phase varying device.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the step of changing the actual cam phase includes changing the actual cam phase with an oil pressure supplied from an oil pressure source, wherein at least one of the time series data of the deviation making up the switching function is multiplied by a multiplication coefficient, and the multiplication coefficient is set in accordance with the oil pressure supplied from the oil pressure source.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the engine control unit, the control program further causes the computer to change the actual cam phase with an oil pressure supplied from an oil pressure source, multiply at least one of the time series data of the deviation making up the switching function by a multiplication coefficient, and set the multiplication coefficient in accordance with the oil pressure supplied from the oil pressure source.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the multiplication coefficient is set such that the deviation decreases at a lower rate as a differential pressure between the oil pressure and a predetermined reference pressure is larger.
In this type of cam phase varying means, it has been confirmed that the actual cam phase optimally converges to the target cam phase when the oil pressure supplied from the oil pressure source is at a predetermined pressure; more susceptible to overshoot the target cam phase as the oil pressure is higher than the predetermined pressure; and more slowly converges to the target cam phase as the oil pressure is lower than the predetermined pressure (see FIG. 6). Therefore, according to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, with the predetermined reference pressure set as the predetermined pressure as mentioned above, the deviation decreases at a lower rate when the oil pressure is higher than the predetermined reference pressure to prevent the actual cam phase from overshooting the target cam phase, whereas the deviation decreases at a higher rate when the oil pressure is lower than the predetermined reference pressure to appropriately increase the rate at which the actual cam phase converges to the target cam phase.
Preferably, in the cam phase control apparatus for an internal combustion engine, the multiplication coefficient is set such that the deviation decreases at a lower rate as a differential pressure between the oil pressure and a predetermined reference pressure is larger.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the multiplication coefficient is set such that the deviation decreases at a lower rate as a differential pressure between the oil pressure and a predetermined reference pressure is larger.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the engine control unit, the multiplication coefficient is set such that the deviation decreases at a lower rate as a differential pressure between the oil pressure and a predetermined reference pressure is larger.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the oil pressure source supplies the cam phase varying means with an oil used in the internal combustion engine, and the multiplication coefficient is set such that the deviation decreases at a lower rate as a shorter time has elapsed from a start of the internal combustion engine.
Generally, in this type of cam phase varying device, the actual cam phase changes more slowly, as the temperature of the oil supplied from the oil pressure source is lower, due to a larger viscous resistance of the oil. Consequently, a degraded responsibility causes an instable behavior of the actual cam phase. For this reason, a low oil temperature may cause an instable behavior of the actual cam phase immediately after the internal combustion engine is started. On the other hand, according to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, since the rate at which the deviation decreases is set lower as a shorter time has elapsed from the start of the internal combustion engine, the responsibility of the control is made lower as the temperature of the oil is lower to make the actual cam phase more susceptible to an instable behavior, thereby making it possible to appropriately converge the actual cam phase to the target cam phase, while compensating the actual cam phase for an instable condition immediately after the start of the internal combustion engine, to ensure the stability for the control.
Preferably, in the cam phase control apparatus for an internal combustion engine, the oil pressure source supplies the cam phase varying device with an oil used in the internal combustion engine, and the multiplication coefficient is set such that the deviation decreases at a lower rate as a shorter time has elapsed from a start of the internal combustion engine.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the oil pressure source supplies an oil used in the internal combustion engine, and the multiplication coefficient is set such that the deviation decreases at a lower rate as a shorter time has elapsed from a start of the internal combustion engine.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the engine control unit, the oil pressure source supplies an oil used in the internal combustion engine, and the multiplication coefficient is set such that the deviation decreases at a lower rate as a shorter time has elapsed from a start of the internal combustion engine.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control apparatus for an internal combustion engine, the cam phase varying means is configured to change the actual cam phase with an oil supplied from an oil pressure source for use by the internal combustion engine, at least one of the time series data of the deviation making up the switching function is multiplied by a multiplication coefficient, and the multiplication coefficient is set such that the deviation decreases at a lower rate as a shorter time has elapsed from a start of the internal combustion engine.
According to this preferred embodiment of the cam phase control apparatus for an internal combustion engine, since the rate at which the deviation decreases is set lower as a shorter time has elapsed from the start of the internal combustion engine, the responsibility of the control is made lower as the temperature of the oil is lower to make the actual cam phase more susceptible to an instable behavior, thereby making it possible to appropriately converge the actual cam phase to the target cam phase, while compensating the actual cam phase for an instable condition immediately after the start of the internal combustion engine, to ensure the stability for the control.
Preferably, in the cam phase control apparatus for an internal combustion engine, the cam phase varying device is configured to change the actual cam phase with an oil supplied from an oil pressure source for use by the internal combustion engine, at least one of the time series data of the deviation making up the switching function is multiplied by a multiplication coefficient, and the multiplication coefficient is set such that the deviation decreases at a lower rate as a shorter time has elapsed from a start of the internal combustion engine.
This preferred embodiment of the cam phase control apparatus provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the cam phase control method for an internal combustion engine, the step of changing the actual cam phase includes changing the actual cam phase with an oil supplied from an oil pressure source for use by the internal combustion engine, wherein at least one of the time series data of the deviation making up the switching function is multiplied by a multiplication coefficient, and the multiplication coefficient is set such that the deviation decreases at a lower rate as a shorter time has elapsed from a start of the internal combustion engine.
This preferred embodiment of the cam phase control method provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.
Preferably, in the engine control unit, the control program further causes the computer to change the actual cam phase with an oil supplied from an oil pressure source for use by the internal combustion engine, multiply at least one of the time series data of the deviation making up the switching function by a multiplication coefficient, and set the multiplication coefficient such that the deviation decreases at a lower rate as a shorter time has elapsed from a start of the internal combustion engine.
This preferred embodiment of the engine control unit provides the same advantageous effects as provided by the corresponding preferred embodiment of the cam phase control apparatus according to the fifth aspect of the invention.